Device for clamping a cutting insert to a seat of a toolholder body

ABSTRACT

A device for clamping a cutting insert to a seat of a toolholder body, said seat having a supporting and a pair of transversely oriented holding surfaces against which the insert is firmly wedged during the threaded engagement of a clamp screw in an inclined threaded opening in the toolholder seat. The inclination of the threaded opening is such as to produce the desired wedging effect against one holding surface during rotative or tightening manipulation of the screw, while said rotative screw movement produces the wedging effect against the other transverse holding surface.

O United States Patent [151 3,673,657

Gustafson et al. July 4, 1972 [54] DEVICE FOR CLAMPING A CUTTING [56]References Cited s ag A UNITED STATES PATENTS 2,930,l ll 3/1960 St.Clair ..29/96 [72] Inventors: Manfred Wallace Gustatson; Torsten San-3,055,13 10 19 2 Gr nl af drud, both of Fagersm, Sweden 3,345,72110/1967 Garih ..29/105 [73] Assignee: Fagersta Bruks Aktiebolag,Fagersta,

Sweden Pnmary Examiner-Harrison L. Hmson Attorney-Bauer and Goodman [22]Filed: Nov. 14, 1969 [2]] App], No.: 876,896 ABSTRACT A device forclamping a cutting insert to a seat of a toolholder [30] ForeignApplication Prio it D t body, said seat having a supporting and a pairof transversely oriented holding surfaces against which the insert isfirmly 3% g g 532? wedged during the threaded engagement of a clampscrew in l we en an inclined threaded opening in the toolholder seat.The 52 U.S. CL ..29/105 "'clmatwn of the threaded p n ng lS such as toproduce the Field ofSearch ..29/96, 105, I05 A desired wedging effectagainst one holding surface during rotative or tightening manipulationof the screw, while said rotative screw movement produces the wedgingefi'ect against the other transverse holding surface.

4 Claims, 7 Drawing Figures vantages of the present invention includesan insert clamping device in the form of a screw head with a peripheralsurface which is essentially conically tapering towards the threadedportion of the screw and is arranged, when the screw is tightened, topress the insert by wedge action in a direction towards a seat holdingsurface by engagement with a side of the cutting insert. That is, thescrew head wedges itself within a progressively diminishing clearancespace between it and the insert and, as a consequence, presses theinsert sufficiently firmly against the seat holding surface to hold theinsert in place during cutting use of the insert.

Given below is a more detailed description of embodiments of theinvention, made with reference to the accompanying drawing, saiddescription disclosing further characterizing features of the invention.

In the drawing:

FIG. 1 is an elevational sectional view of a mill with a clamping deviceaccording to the invention, the cutting insert being in an unclampedcondition;

FIG. 2 is a view similar to FIG. 1 showing the clamping device in theposition of clamping the cutting insert;

FIG. 3 is a plan view of the clamping device according to FIGS. 1 and 2;

FIGS. 4-7 illustrate additional embodiments, to wit:

FIGS. 4 and 5 are front elevational sectional views of exemplaryclamping devices; and

FIGS. 6 and 7 are side elevational views, in section, taken along lines6-6 of FIG. 4 and line 7-7 of FIG. 5, respectively.

EMBODIMENT OF FIGS. 1-3

In FIGS. 1 through 3, 10 refers to a portion of the toolholder body of amill, the axis of rotation of which extending essentiallyperpendicularly to the planes of FIGS. 1 and 2. Portion 10 has a recess11, in which is formed a seat for a cutting insert 12. The seat isformed by a first holding surface 14 for one of the side walls or broadsides 15 of the insert, said first holding surface 14 in the illustratedembodiment being formed on a separate anvil 13. Seat 11 also includes asupporting type surface 16 and a second holding surface 17 forsupporting two of the edge sides 18 essentially in the radial and axialdirection, respectively. In a lengthwise partly tapped opening 19disposed adjacent the seated position of the insert 12, the axis of saidopening forming an acute and preferably small angle with the broad sides15 of the cutting insert 12, there is disposed a clamp screw 21, thehead 22 of which is adapted to abut the broad side of the cutting insertfacing outwardly from the first holding surface 14 in order to urge thecutting insert, when said screw is tightened, through movement in adirection towards said first holding surface 14, said supports surface16, 17 said second holding surface.

The screw head has a conical surface which is essentially taperingtowards the threaded portion of the screw and is adapted to urge theinsert by wedge action in a direction towards the surface 14, when thescrew is tightened, by engagement with the side of the insert 12 facedfrom said surface. On its other side the screw head engages a further orthird holding surface 25 of the portion 10, said holding surface beinginclined essentially in correspondence with said conical surface.Furthermore, the mutual disposition of the seat 14, 16, 17, the opening19 and the surface 25 is such, that, when the screw is tightened, theconical surface 24 will establish contact with said surface 25. In otherwords, the radical distance between a position on the axis of theopening 19 and the broad side of the insert 12 faced to the screw isless than the radical distance between said position and the surface 25.In FIG. 1 is shown the position of the device at the beginning of thetightening of the screw 21, the surface 24 of the left hand threadedscrew, owing to the rotation of the screw, urging the cutting insertthrough movement in a direction towards the second holding surface 17and, owing to the movement of the screw into the opening 19, urging thecutting insert in a direction towards the support surface 16. In FIG. 2the device is shown in a position in which the surface 24 has ultimatelyreached contact with said third holding surface 25 of the mill body, anda high clamping pressure is achieved on the cutting insert withoutapplying any heavy stresses to the threads of the screw 21 and those ofthe opening 19.

According to FIGS. 1 through 3, the supporting surface 14 is fonned on aseparate anvil 13 supported by a surface 26 of the mill body. It is,however, within the scope of the invention to arrange the supportingsurface for the anvil on a separate toolholder clampable in the millbody, as known per se, and also to omit said anvil and permit bodysurface 26 to perform its function. Furthermore, a chipbreaker, asindicated at 28 in the FIG. 7 embodiment, could be arranged between thecutting insert 12 and the conical surface 24 of the screw 21.

The conical surface 24 of the screw head 22 is preferably inclined toprovide linear contact with the cutting insert 12 or with thechipbreaker, if any, respectively, and also with the surface 25 of themill body. The surface 24 is advantageously provided with a top grippingarea of relatively small length, as shown at 24, and the surface 25could preferably be formed by the side wall of a conically shapedcounterbore in the opening 19, the outer end surface 27 of the screwhead 22 preferably covering the mouth of the opening 19 as completely aspossible when the screw 21 clamps the insert 12, as shown in FIGS. 2 and3.

When tightening the screw 21, in order to delay the time of wedgingcontact between the surface 24 and the cutting inset 12 until entry ofthis surface below the level of the surface 25, in accordance with anembodiment of the invention, there is advantageously provided a certainamount of clearance between the threads of the screw 21 and those of theopening 19. Thus, in response to the engagement of the surface 24 withthe cutting insert, when said tightening takes place, the screw ispivoted to a position in which the surface establishes said contact withthe reaction surface 25. This condition is shown in FIGS. 1 and 2. InFIG. 1 there is a lengthwise essentially equally formed clearance 28along the portion 23 between the threads of the screw 21 and those ofthe opening 19 and the axis of the screw coincides with the axis 20 ofthe opening. In FIG. 2 the screw 21 has been pivoted in a directiontowards the surface 25 whereby a clearance no longer exists between saidthreads at the upper left and the lower right portion, as seen in FIG.2, of the area in which the threads of the screw are in engagement withthose of the opening, the axis 29 of the screw being inclined to theaxis 20 of the opening. However, the same effect can be achieved bymaking the shank of the screw flexible to a certain extent so that theclamp screw is bent until the surface 24 establishes contact with thereaction surface of the mill body, and it is also within the scope ofthe invention to form the device in a manner causing said movement ofthe surface 24 towards the surface 25 to take place during a combinedpivoting and bending of the screw.

Although the just described clamping embodiment is useful with a milland a positive rake insert, it is not limited to this use but may beused together with other types of cutting tools with mechanicallyclamped cutting inserts as well as in connection with negative rakeinserts.

EMBODIMENTS OF FIGS. 4-7

In FIGS. 4 and 6, the part 10' has a recess 11 where a seat for anindexable insert 12' is constructed. The seat is formed of first holdingsurface 14 for one of the broad sides 15' of the insert, constructed ona separate anvil 13' and a second holding surface 16' a supporting typesurface and 17' in order to support two of the edge sides 18' of theinsert mainly in the axial and radial direction respectively of themilling cutter. In a hole 19', threaded along part of its length,located beside the seat in the tool body the center axis of which formsa sharp and preferably small angle with the broad sides of the insert12', a locking screw is attached, the head of which is arranged to acton the broad side of the insert, turned away from the first holdingsurface 14, and in order to press the insert at the tightening of thescrew in the direction of the first holding surface 14 .and the secondholding surface 16', supporting type surface 17'.

The screw head 21 has both a mainly cylindrical casing surface 22' andalso a casing surface 24 that is mainly tapering comically to thethreaded part 23' of the screw 20'. The conical casing surface 24' whichis located preferably close to the cylindrical casing surface 22', isarranged so as to press the insert 12' at the tightening of the screw20' through the Wedge efi'ect in the direction of the supporting face,whilst the force of reaction is absorbed at the side of the screw head21' opposite to' the insert, mainly only by means of the cylindricalcasing surface 22' resting against a surface 25' on the part 10',running mainly parallel with the axis of the hole 19'. The screw 20' isthen assumed to be left-hand by means of which the conical casingsurface 24 at the tightening of the screw, on account of the rotation ofthe screw acts on the insert in the direction of the second holdingsurface 16' and on account of the motion of the screw into the hole 19'acts on the insert in the direction of the support surface 17' so as toensure that it rests correctly against the surfaces 16, 17'.

According to FIGS. 4 and 6, the first holding surface 14', isconstructed on a separate anvil 13' which rests against a surface 26 onthe body of the milling cutter. However, it lies within the scope of theinvention to arrange, in a known manner, the supporting face for theanvil on a separate toolholder that can be clamped on the body of themilling cutter, also to leave out the anvil and to construct thesupporting surface for the anvil directly on the body of the millingcutter or the toolholder, if any. Furthermore, between the insert 12 andthe casing surface 24' of the screw head 21 a chipbreaker can bearranged.

To illustrate the above possibilities of variation, a device is shownin'FlGS. 4 and 7, differing from the device according to FIGS. 4 and 5onlythereby that the seat for the insert 12 is arranged on a separatetoolholder 27' and that the conical cas' ing surface 24 of the lockingscrew 20 acts on the insert via a chipbreaker 28'. The toolholder andthe chipbreaker extending along the holder are received in a mainlyaxial slot 29' in the body of the milling cutter and are supposed to becapable of being clamped in an ordinary manner in the slot 29 with theaid of a clamping device (not shown), such as a wedge or a screw similarto the above, besides with the aid of the shown screw 20'. The radialsupport 17' for the insert is arranged on the body of the milling cutterwhilst the axial support 30' and the supporting face 31' for the insertare constructed directly on the toolholder.

The conical casing surface 24' of the screw head 21 has contact with theinsert 12' or with the chipbreaker 28, if any, as shown. The reactionsurface 25 can be formed advantageously of the side wall of an enlarged,cylindrical counterbore opening of the hole 19' and it is thenfavorably, if the opening part mentioned has a diameter, only slightlyexceeding the diameter of the cylindrical casing surface 22', and if theexternal end surface 32 of the screw head is located by the opening ofthe hole 19 when the screw 20' locks the insert 12, as shown in FIGS. 6and 7.

A latitude of modification, change and substitution is intended in theforegoing disclosure and in some instances some features of theinvention will be employed without a corresponding use of otherfeatures.

We claim:

1. A toolholder construction comprising:

a toolholder body 10) having a means (16) defining an insert sup rtsurface and a pair of transverse] oriented first (l4 and second (17)holding surfaces bor ering said support surface defining means l6) andcooperating therewith to define a tool insert seat 1 l a tool insert(12) of a prescribed shape presenting an opposite fust and second pairof side walls l5) and an end wall (18) therebetween operatively mountedon said support surface defining means (16) within said insert seat(11), with said second side wall (15) and said end wall (18) in looseengagement respectively against said first (l4) and second (17) holdingsurfaces,

said tool holder body (10) having a threaded opening (19) thereinlocated adjacent to said support surface defining means l6) and adjacentsaid tool insert 12) in said mounted position thereof and angularlyoriented in the direction of saidifirst (14) holding surface effectiveto define a clearance space of a progressively diminishing extentbetween the longitudinal center of said threaded opening (19) and saidfirst holding surface (14),

said threaded opening (19) having a partial, counterbore in said upperend efi'ective to provide an angularly inclined third holding surface(25) in facing relation to said first holding surface (14), and

a threaded member (21) with a round head having an operative position inthreaded engagement within said threaded opening (19) incident torotation thereof effecting said threaded engagement,

said head of said threaded member being rotatable to said operativeposition wherein said head of said threaded member (21) is in directabutment against said first side wall (15) of said tool insert 12) inwedge relation between said facing first l4) and third (25) holdingsurfaces and said tool insert end wall (18) in seated relationagainst'said second holding surface (17), whereby said wedged relationresults from wedging movement of said head of said threaded member (21)through said clearance space of progressively diminishing extent andsaid seated relation from rotation of said head of said threaded member(21) in the direction of said second holding surface (17) during saidwedging movement.

2. A toolholder construction as defined in claim 1 including an anvilmember mounted in an interposed position between said tool insert (12)and said toolholder body (10).

3. A toolholder construction as defined in claim 1 wherein said partialcounterbore is conical and wherein said round head of said threadedmember 21) is conical.

4. A toolholder construction as defined in claim 1 wherein said partialcounterbore is cylindrical and wherein said round head of said threadedmember (21) is cylindrical.

1. A toolholder construction comprising: a toolholder body (10) having ameans (16) defining an insert support surface and a pair of transverselyoriented first (14) and second (17) holding surfaces bordering saidsupport surface defining means (16) and cooperating therewith to definea tool insert seat (11), a tool insert (12) of a prescribed shapepresenting an opposite first and second pair of side walls (15) and anend wall (18) therebetween operatively mounted on said support surfacedefining means (16) within said insert seat (11), with said second sidewall (15) and said end wall (18) in loose engagement respectivelyagainst said first (14) and second (17) holding surfaces, said toolholder body (10) having a threaded opening (19) therein located adjacentto said support surface defining means (16) and adjacent said toolinsert (12) in said mounted position thereof and angularly oriented inthe direction of said first (14) holding surface effective to define aclearance space of a progressively diminishing extent between thelongitudinal center of said threaded opening (19) and said first holdingsurface (14), said threaded opening (19) having a partial counterbore insaid upper end effective to provide an angularly inclined third holdingsurface (25) in facing relation to said first holding surface (14), anda threaded member (21) with a round head having an operative position inthreaded engagement within said threaded opening (19) incident torotation thereof effecting said threaded engagement, said head of saidthreaded member being rotatable to said operative position wherein saidhead of said threaded member (21) is in direct abutment against saidfirst side wall (15) of said tool insert (12) in wedge relation betweensaid facing first (14) and third (25) holding surfaces and said toolinsert end wall (18) in seated relation against said second holdingsurface (17), whereby said wedged relation results from wedging movementof said head of said threaded member (21) through said clearance spaceof progressively diminishing extent and said seated relation fromrotation of said head of said threaded member (21) in the direction ofsaid second holding surface (17) during said wedging movement.
 2. Atoolholder construction as defined in claim 1 including an anvil membermounted in an interposed position between said tool insert (12) and saidtoolholder body (10).
 3. A toolholder construction as defined in claim 1wherein said partial counterbore is conical and wherein said round headof said threaded member (21) is conical.
 4. A toolholder construction asdefined in claim 1 wherein said partial counterbore is cylindrical andwherein said round head of said threaded member (21) is cylindrical.